1. Field of the Invention
The present invention relates to a cutter for use in an electric razor and more particularly to a cutter, the edge line of which is spiral and a method for manufacturing the cutter and in addition, a molding die for manufacturing the cutter.
2. Description of the Related Arts
Japanese Utility Model Laid-Open Publication No. 2-67969 has disclosed a spiral cutter machined from an annular or cylindrical material by using a hobbing machine, with the spiral cutter being used as the internal blade of an electric razor.
Japanese Patent Laid-Open Publication No. 2-67969 has disclosed the internal blade, of an electric razor, molded by axially inserting a straight band-shaped blade into the peripheral surface of a base for holding the blade with the blade not elastically deformed.
The above-described conventional spiral cutter machined from a material by using a hobbing machine cuts well, but the productivity thereof is low and hence the manufacturing cost is high.
The above-described conventional blade is molded by inserting the band-shaped blade into the base, so that mass production thereof is possible. But the thin band-shaped blade is subject to resistance caused by a mustache, and will likely flex to a great extent. Therefore, the cutting performance is deteriorated. The flexure of the band-shaped blade can be reduced to a great extent by reducing the height of the band-shaped blade with respect to the peripheral surface of the base, but the following problems occur: The space formed between the fixed external blade and the peripheral surface of the base is narrow. As a result, it is difficult to introduce a long mustache into the blade and the cut mustache hair are likely to be blown out from the mustache introducing openings of the fixed external blade. Thus, the height of the band-shaped blade with respect to the peripheral surface of the base cannot be too small. The flexure of the band-shaped blade can be prevented to a certain extent by thickening the band-shaped blade, but sliding resistance will increase due to the increase of the contact area between the inner surface of the fixed external blade and the band-shaped blade. Consequently, an overload is applied to the motor and it is difficult to obtain the plasticity of a desired configuration and to carry out a pressing operation.
In order to solve the above-described problems, Japanese Patent Laid-Open Publication No. 58-173677 has disclosed a spiral cutter wound around a holding groove provided on the peripheral surface of a drum by crimping both ends thereof onto the groove, i.e., the spiral cutter is fixed to the groove at only both ends thereof while the region between both ends thereof is held inside the groove. Therefore, the spiral cutter is likely to shake and incline. In addition, since a single blade is wound around the drum, the torsional angle is at least 50.degree.. Consequently, the performance of the blade is similar to that of an unsharp end blade.
A spiral cutter according to Japanese Patent Laid-Open Publication No. 59-44970 comprises a plurality of blades. Each blade is fixed to a base at both ends thereof and the region between both ends is likely to incline and be moved due to sliding resistance and cutting resistance in a manner to the above-described conventional art. That is, the blade does not provide a clean cut.